Communication in a wireless network using restricted bandwidths

ABSTRACT

The base station (BS) may transmit a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcast channel (PBCH) including a master information block (MIB). Further, the PSS, SSS and PBCH are in a first bandwidth of a cell having a cell bandwidth, wherein the first bandwidth is a first portion of the cell bandwidth. The MIB includes an indication of frequency resources and time resources for use by user equipments (UEs) to acquire additional system information. The BS may transmit control information using the indication of the frequency resources and the time resources for the UEs to acquire the additional system information.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/190,420, filed Nov. 14, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/372,363, filed Jul. 15, 2014, now abandoned,which is a § 371 application of International Application No.PCT/GB2013/050126, filed Jan. 21, 2013, which are incorporated byreference as if fully set forth.

FIELD OF INVENTION

The present invention relates to wireless communications systems andmethods, and in particular to a system, method, base station andterminal device for communicating using a subordinate carrier of a hostcarrier.

BACKGROUND OF THE INVENTION

Mobile communication systems have evolved over the past ten years or sofrom the GSM System (Global System for Mobile communications) to the 3Gsystem and now include packet data communications as well as circuitswitched communications. The third generation partnership project (3GPP)is developing a fourth generation mobile communication system referredto as Long Term Evolution (LTE) in which a core network part has beenevolved to form a more simplified architecture based on a merging ofcomponents of earlier mobile radio network architectures and a radioaccess interface which is based on Orthogonal Frequency DivisionMultiplexing (OFDM) on the downlink and Single Carrier FrequencyDivision Multiple Access (SC-FDMA) on the uplink.

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architectures, are able to support a more sophisticated range ofservices than simple voice and messaging services offered by previousgenerations of mobile telecommunication systems.

For example, with the improved radio interface and enhanced data ratesprovided by LTE systems, a user is able to enjoy high data rateapplications such as mobile video streaming and mobile videoconferencing that would previously only have been available via a fixedline data connection. The demand to deploy third and fourth generationnetworks is therefore strong and the coverage area of these networks,i.e. geographic locations where access to the networks is possible, isexpected to increase rapidly.

The anticipated widespread deployment of third and fourth generationnetworks has led to the parallel development of a class of devices andapplications which, rather than taking advantage of the high data ratesavailable, instead take advantage of the robust radio interface andincreasing ubiquity of the coverage area. Examples include so-calledmachine type communication (MTC) applications, also known asmachine-to-machine (M2M) communications, some of which are in somerespects typified by semi-autonomous or autonomous wirelesscommunication devices (i.e. MTC devices) communicating small amounts ofdata on a relatively infrequent basis. Examples include so-called smartmeters which, for example, are located in a customer's home andperiodically transmit data back to a central MTC server relating to thecustomer's consumption of a utility such as gas, water, electricity andso on.

Whilst it can be convenient for a terminal such as an MTC-type terminalto take advantage of the wide coverage area provided by a third orfourth generation mobile telecommunication network there are at presentdisadvantages. Unlike a conventional third or fourth generation mobileterminal such as a smartphone, a primary driver for MTC-type terminalswill be a desire for such terminals to be relatively simple andinexpensive. The type of functions typically performed by a MTC-typeterminal (e.g. simple collection and reporting of relatively smallamounts of data) do not require particularly complex processing toperform, for example, compared to a smartphone supporting videostreaming. However, third and fourth generation mobile telecommunicationnetworks typically employ advanced data modulation techniques andsupport wide bandwidth usage on the radio interface which can requiremore complex and expensive radio transceivers to implement. It isusually justified to include such complex transceivers in a smartphoneas a smartphone will typically require a powerful processor to performtypical smartphone type functions. However, as indicated above, there isnow a desire to use relatively inexpensive and less complex devices tocommunicate using LTE type networks.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided awireless communications system, comprising a base station, one or moreterminal devices of a first type and one or more terminal devices of asecond type. The base station is operable to communicate with theterminal devices of the first type using a host carrier comprising radioresource segments distributed in time, each radio resource segmentproviding radio resources across a first frequency band. The basestation is operable to communicate with the terminal devices of thesecond type using a subordinate carrier comprising radio resourceswithin a second frequency band of a subset of the radio resourcesegments of the host carrier, the second frequency band being narrowerthan and contained within the first frequency band.

In this way, an efficient and flexible mechanism for specifying andcontrolling an amount and location of radio resources to be dedicated toa subordinate earner for use by a particular (e.g. reduced capability)type of device can be provided.

One way of achieving this differentiated access between the terminaldevices of the first type and second type is to allocate a part of thecarrier resource that is dedicated to the second type of device (e.g.MTC traffic) using normal eNB (base station) scheduling. The eNBdifferentiates between MTC and non-MTC (example of the first type ofdevice) UEs and only schedules MTC UEs within the reserved part of theearner resource and only schedules non-MTC UEs outside of the reservedpart of the carrier resource. While this solution is viable, the simplescheduling approach places some restrictions on the MTC subordinatecarrier that can be realised. For instance, it would be necessary to usethe same carrier characteristics and/or reference signals. If it wereadvantageous to use different carrier characteristics or to useadditional or modified reference signals then this may not be possiblein an MTC subordinate carrier implemented purely by eNB scheduling.

The radio resource segments may be sub-frames of radio frames, eachradio frame comprising a plurality of sub-frames. In this case, thesub-frames may be allocated to the subordinate carrier using asubordinate carrier sub-frame allocation set, the subordinate carriersub-frame allocation set determining which sub frames within a repeatinggroup of one or more radio frames are allocated to the subordinatecarrier. The subordinate carrier sub-frame allocation set may be definedby one or more reserved sub-frame allocation patterns. The one or morereserved sub-frame allocation patterns may comprise all or a sub-set ofall reserved sub-frame allocation patterns defined for the host carrier.

In one example, the subframes selected for the subordinate carrier areso-called MBSFN (Multimedia Broadcast/multicast service over a SingleFrequency Network) subframes. This embodiment relies on the fact thatsuch subframes do not have to be used exclusively for MBSFN. The LTERel. 8/9/10 specifications define a means (in the standard LTESystemInformationBlockType2—SIB2) by which certain subframes can beexcluded from normal allocation to the Physical Downlink Shared Channel(PDSCH). Furthermore, the specifications define signalling within thestandard system information which allows some or all of these excludedsubframes to be used for other defined purposes, such as MBMS (inSystemInformationBlockType13—SIB 13), relay and positioning referencesignal transmission. However, reading of this system information mayrequire reception across the whole carrier bandwidth.

Acquisition information required for a terminal device of the secondtype to receive the subordinate carrier may be allocated for inclusionin sub-frames of the subordinate carrier using at least a portion of thesubframes in one or more of the reserved sub-frame allocation patternsdefining the subordinate carrier.

The base station may be operable to transmit an indication of the radioresources of all reserved sub-frames to terminal devices of the firsttype. In this way, the first type of device is informed of subframeswhich are reserved for the subordinate carrier, another subordinatecarrier, and for other purposes such as relay backhaul. A particulardevice of the first type is not required to know why a particularsub-frame is reserved, merely that it is not available to that device.This indication may be presented to the terminal devices of the firsttype as a reserved subframe allocation within a system information blocktransmitted using frequency resources not necessarily limited to thesecond frequency band of the subordinate carrier. In this way, it ispossible to exclude non-MTC devices from a resource reserved for thesubordinate carrier.

The base station may be operable to transmit, using radio resourceswithin the second frequency band, subordinate carrier informationindicating that a subordinate carrier is available within the hostcarrier. A terminal device of the second type may be responsive tosubordinate carrier information indicating that a subordinate carrier isnot available within the host carrier to terminate a camp-on procedurefor camping on to the network.

The subordinate carrier information may be provided within firstacquisition information transmitted on radio resources within the secondfrequency band, the first acquisition information being required for aterminal device of the first type to receive the system information ofthe host carrier. The first acquisition information may be a masterinformation block transmitted on a physical broadcast channel withinradio resources of the host earner. In this way it is possible to signalvia the first acquisition information, to terminal devices of the secondtype, the presence of an MTC subordinate carrier existing within thereserved resource and using only a restricted bandwidth. If thesubordinate carrier information is not present then the camp-on processby a terminal device may be terminated early, thereby reducing time andpower wastage at the terminal device.

The first type of terminal device may be capable of receiving the fullbandwidth of the first frequency band, and the second type of terminaldevice may not be capable of receiving the full bandwidth of the firstfrequency band but be capable of receiving the full bandwidth of thesecond frequency band. The bandwidth of the subordinate carrier may bepredetermined and be known in advance to terminal devices of the secondtype. Alternatively, the base station may be operable to transmit, usingradio resources within the second frequency band, an indication of thebandwidth of the subordinate carrier. In this case the bandwidth neednot necessarily be predetermined. The indication of the bandwidth of thesubordinate carrier may be provided within first acquisition informationtransmitted on radio resources within the second frequency band, theacquisition information being provided to permit a terminal device ofthe first type to receive the host carrier downlink and camp on to thehost carrier. Alternatively, the base station may be operable totransmit, using radio resources of the subordinate carrier, anindication of the bandwidth of the subordinate carrier.

The base station may be operable to transmit, using radio resources ofthe subordinate carrier, second acquisition information required for aterminal device of the second type to receive the subordinate carrierdownlink and camp on to the subordinate carrier. The second acquisitioninformation may be transmitted on predetermined radio resources whichare known in advance to terminal devices of the second type. The secondacquisition information may comprise an indication of the bandwidth ofthe subordinate carrier. In this way, it is possible to signal systeminformation defining the characteristics of the MTC subordinate carrierusing only resources within the MTC subordinate carrier.

The radio resource segments may be sub-frames of radio frames in thetime direction, each radio frame comprising a plurality of sub-frames.The second acquisition information may be transmitted in at least someof the sub-frames allocated to the subordinate carrier. A terminaldevice of the second type may be operable to determine whether asub-frame contains second acquisition information from a current radioframe number and a first sub-frame allocation set for allocating thesecond acquisition information to sub-frames within the subordinatecarrier, said first sub-frame allocation set identifying whichsub-frames within a repeating group of one or more radio frames containthe second acquisition information.

The current radio frame number may be determined from first acquisitioninformation transmitted on radio resources within the second frequencyband, the first acquisition information being required for a terminaldevice of the first type to receive the host carrier downlink and campon to the network. The first sub-frame allocation set may bepredetermined and known in advance to terminal devices of the secondtype. The second acquisition information may comprise an indication ofthe current radio frame number. Accordingly, once the second acquisitioninformation is available to a mobile terminal, it may from that point onobtain the current radio frame number from the second acquisitioninformation rather than having to refer back to the first acquisitioninformation.

A terminal device of the second type may be operable to determinewhether a sub-frame is allocated to the subordinate carrier from acurrent radio frame number and a second sub-frame allocation set for thesubordinate carrier, said second sub-frame allocation set identifyingwhich sub-frames within a repeating group of one or more radio framesare allocated to the subordinate carrier. The current radio frame numbermay be determined from the second acquisition information.Alternatively, the current radio frame number may be determined from thefirst acquisition information and updated by counting radio frames.

The second sub-frame allocation set may be predetermined and known inadvance to terminal devices of the second type. Alternatively, thesecond sub-frame allocation set may be specified in the secondacquisition information. It will be appreciated that the secondsub-frame allocation set may be different to the first sub-frameallocation set, but will include all of the sub-frames of the firstsub-frame allocation set (and probably additional sub-frames as well).

The first type of terminal device may be an LTE device and the secondtype of device may be a low data rate device. The first type of terminaldevice may be an LTE device and the second type of device may be a lowdata rate device for providing machine-to-machine (M2M) communication.

It will be appreciated that different radio resource segments of thesame or a different frequency band may be used to support a furthersubordinate carrier.

At least a portion of the radio resources outside of the secondfrequency band of the subset of the radio resource segments of the hostearner allocated to the subordinate carrier may be allocated to anothersubordinate carrier. In other words, a different frequency band of thesame resource segments (in time) may support another carrier.

At least a portion of the radio resources outside of the secondfrequency band of the subset of the radio resource segments of the hostcarrier allocated to the subordinate carrier may be used forcommunicating with terminal devices of the first type. In other words, adifferent frequency band of the same resource segments (in time) maysupport the host carrier.

Viewed from another aspect, there is provided a base station forcommunicating with terminal devices. The base station is operable tocommunicate with terminal devices of a first type using a host carriercomprising radio resource segments distributed in time, each radioresource segment providing radio resources across a first frequencyband. The base station is operable to communicate with terminal devicesof a second type using a subordinate carrier comprising radio resourceswithin a second frequency band of a subset of the radio resourcesegments of the host carrier, the second frequency band being narrowerthan and contained within the first frequency band.

Viewed from another aspect, there is provided a terminal device forcommunicating with a base station which supports a host carriercomprising radio resource segments distributed in time, each radioresource segment providing radio resources across a first frequencyband. The terminal device is operable to communicate with the basestation using a subordinate carrier comprising radio resources within asecond frequency band of a subset of the radio resource segments of thehost carrier, the second frequency band being narrower than andcontained within the first frequency band.

Viewed from another aspect, there is provided a method of communicatingbetween a base station and terminal devices of a first type and a secondtype. The method comprises communicating between the base station andterminal devices of a first type using a host carrier comprising radioresource segments distributed in time, each radio resource segmentproviding radio resources across a first frequency band, andcommunicating between the base station and terminal devices of a secondtype using a subordinate carrier comprising radio resources within asecond frequency band of a subset of the radio resource segments of thehost carrier, the second frequency band being narrower than andcontained within the first frequency band.

Viewed from another aspect, there is provided a method of communicatingwith a base station from a terminal device, comprising communicatingwith the base station using a subordinate carrier of a host carriercomprising radio resource segments distributed in time, each radioresource segment of the host carrier providing radio resources across afirst frequency band, the subordinate carrier comprising radio resourceswithin a second frequency band of a subset of the radio resourcesegments of the host carrier, the second frequency band being narrowerthan and contained within the first frequency band.

It will be appreciated that features of the above-described aspects andembodiments of the invention may be combined with features of otheraspects and embodiments of the invention as appropriate and incombinations other than those explicitly set out. For example, optionalfeatures of the first aspect of the invention may equally optionally beincorporated in embodiments according to other aspects of the invention,for example where the different aspects have corresponding features.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will now be described withreference to the accompanying drawings in which like parts have the samedesignated references and in which:

FIG. 1 is a schematic block diagram of a radio network and a pluralityof user equipments forming a wireless communication system whichoperates in accordance with the 3GPP Long Term Evolution (LTE) standard;

FIG. 2 schematically represents elements of a mobile telecommunicationssystem for implementing embodiments of the invention;

FIG. 3 schematically represents a time and frequency resource allocationbetween a host carrier and a subordinate carrier;

FIG. 4 schematically illustrates a radio frame and resource gridstructure of time and frequency resources;

FIGS. 5A to 5D schematically illustrate example allocations of resourcesto the subordinate carrier;

FIG. 6 is a schematic flow diagram of a first part of a camp-onprocedure for connecting to the subordinate carrier;

FIG. 7 is a schematic flow diagram of a second part of the camp-onprocedure for connecting to the subordinate carrier; and

FIG. 8 schematically illustrates a signalling configuration according toan embodiment of the invention.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS Network Structure

Embodiments of the present invention are described herein withparticular reference to an example implementation in a wirelesscommunication system having carriers based around the 3GPP Long TermEvolution (LTE) standard.

FIG. 1 schematically shows an example architecture of an LTE system. TheLTE system is provided by a telecommunications network operator to allowparties to communicate. As shown in FIG. 1, mobile communicationsdevices designated as user equipment (UE) 105 are arranged tocommunicate data to and from base stations (transceiver stations) 101which are frequently referred to in LTE as E-UTRAN NodeBs (e-nodeB).Each of the base stations 101 comprises a transceiver unit 103 enablingcommunication of data to and from a plurality of mobile communicationdevices via a radio interface. The e-nodeBs 101 are connected to aserving gateway S-GW 104 and to a mobility management entity (MME) 107.The S-GW 104 is arranged to perform routing and management of mobilecommunications services to the communications devices 105 in the mobileradio network. In order to maintain mobility management andconnectivity, the mobility management entity (MME) 107 manages evolvedpacket system (EPS) connections with the communications devices 105using subscriber information stored in a home subscriber server (HSS)108. Other core network components include a packet data network gateway(P-GW) 106 which connects to an internet network 109 and finally to anexternal server (not shown). In the context of MTC communications a UEsupporting MTC communications may, for example, be conveniently referredto as an MTC terminal or MTC UE, and a server with which the MTCterminal(s) communicate data may, for example, be conveniently referredto as an MTC server. More generally, devices in the system capable ofsupporting MTC communications may be referred to as MTC entities. Thevarious elements of FIG. 1 and their respective modes of operation arewell-known and defined in the relevant standards administered by the3GPP® body and also described in many books on the subject, for example,Holma H. and Toskala A [1]. These conventional aspects of LTE networksare not described further in the interest of brevity.

Two classes of device are considered herein. A first class of device isconfigured to communicate via a host carrier, and a second class ofdevice is configured to communicate via a subordinate carrier. In someof the particular examples considered here, the first class of deviceand the host carrier are compliant with particular standards, forexample, LTE Rel. 8/9/10 standards, and the second class of device andthe subordinate carrier are compliant with modified versions of theseparticular standards, for example, based on versions of the standardsmodified to support lower-capability devices. Accordingly, and purelyfor the sake of reference and to aid explanation, the first class ofdevice and the host carrier may be referred to here in some examples aslegacy devices and legacy carrier, while the second class of device andthe subordinate carrier may be referred to in some examples as MTCdevices and MTC carrier (or in alternative DMN (Dedicated MessagingNetwork) devices and DMN carrier). However, it will be appreciated thatthese terms are simply used as labels for ease of explanation ofparticular implementations of embodiments of the invention fordistinguishing the two classes of device and carrier. Thus, the term“legacy” should not be considered as indicating any form ofobsolescence, and indeed the devices and carrier(s) referred to here aslegacy devices and carrier(s) may equally correspond with devices andcarrier(s) that comply with future releases of the LTE standards, forexamples Rel. 11 and beyond. Equally, and as already noted above, DMNshould not be taken to refer to a network which exclusively supportsonly basic messaging services. Furthermore, the second class of deviceand subordinate carrier that are described here as not being fullycompliant with the operating standards of the first class of device andfirst carrier (for example because of reduced capability) maynonetheless be compliant with their own standards. Furthermore, thefunctionality described herein as regards both the first and secondclasses of device and carriers might comply with different aspects of afuture standard, for example a future release of the LTE standards.

Referring now to FIG. 2, a base station 101′ is shown communicativelyconnected to an LTE device 105 a via a transceiver unit 103′ and a first(host) earner 110 a, and communicatively connected to an MTC device 105b via the transceiver unit 103′ and a second (subordinate) carrier 110b. The base station 101′ is responsible for a coverage area in whichboth the LTE device 105 a and the MTC device 105 b are located. Thesingle base station 101′ is able to communicate on both the firstcarrier 110 a and the second carrier 110 b. The first carrier 110 a is ahost carrier having a broad bandwidth, while the second carrier 110 b isa subordinate carrier having a narrower bandwidth located within thefrequency band of the host earner. As will be explained in more detailbelow, the time and frequency resources of the first (host) carrier andthe second (subordinate) carrier are logically separate for the purposesof data transmission and most control signalling, but some time andfrequency resources are accessible to and used by devices connected toboth the first and second carriers.

Host Carrier and Subordinate Carrier Overview

Referring to FIG. 3, the time and frequency resources constituting thehost carrier and the subordinate carrier are schematically illustrated.The horizontal axis of FIG. 3 is time, with a time period from t₁ to t₂being shown in FIG. 3. The vertical axis of FIG. 3 is frequency, thefrequency increasing from a frequency f₁ to a frequency f₄. The hostcarrier has a frequency band F₁, extending from the frequency f₁ to thefrequency f₄. The subordinate earner has a frequency band F₂, extendingfrom a frequency f₂ to a frequency f₃. The subordinate carrier isintended primarily for use by terminal devices which do not have thecapability to receive or transmit between the frequencies f₁ and f₂, andbetween the frequencies f₃ and f₄. The subordinate carrier does notoccupy all of the time and frequency resources within the frequency bandF₂. Instead, certain time periods 305 of the frequency band F₂ areallocated to the subordinate carrier (and potentially to othersubordinate carriers), with the unallocated time periods within thefrequency band F₂ forming part of the host carrier resources. The shadedportions 310 of FIG. 3 indicates those time and frequency resourcesallocated to the subordinate carrier. When a time period 305 isallocated to the subordinate carrier, the time and frequency resources315 falling outside of the frequency band F₂ (but within the frequencyband F₁) are not allocated to the subordinate carrier. In someimplementations these time and frequency resources may be available tothe host carrier (or to another subordinate earner having a different(and non-overlapping) frequency band). In other implementations thesetime and frequency resources may be “lost” and unusable by either thefirst type of device or the second type of device. It is envisaged thatthe central frequency and bandwidth of the frequency bands F₁ and F₂would be fixed for a given host carrier/subordinate carrier, althoughimplementations in which they are not fixed may be possible. Theparticular time periods allocated to the subordinate carrier may befixed, or may be dynamically variable, for example to increase ordecrease the amount of radio resources allocated to the subordinatecarrier to adapt to traffic conditions of the subordinate carrier(and/or possibly of the host carrier).

Radio Frame and Resource Grid Structure

Referring now to FIG. 4, a radio frame and resource grid structure foran LTE type network is schematically illustrated. At the top of FIG. 4,a radio frame 410 is shown. This occupies the full width of thefrequency band of the host carrier, and has a duration of 10 ms. Theradio frame 410 is one of a sequence of radio frames which are used tocommunicate data between a base station and a terminal device. The radioframe 410 comprises 10 sub-frames 420, which again occupy the fullywidth of the frequency band of the host carrier. Each of thesesub-frames 420 has a duration of 1 ms. Each of the sub-frames 420comprises two slots 430, each slot occupying the full width of thefrequency band of the host carrier and having a duration of 0.5 ms. Eachslot comprises a plurality of resource blocks 440 in the frequencydirection, and only a single resource block 440 in the time direction.In other words each resource block 440 has a duration of 0.5 ms (thesame as the duration of the slot 430), but occupies only a portion ofthe bandwidth of the host carrier. Each resource block 440 comprises atwo-dimensional array of resource elements 450 distributed in both thetime direction and the frequency direction. Each resource element 450has a length (duration) of one modulation symbol, and a frequency rangeof one subcarrier (e.g. 15 kHz). In the present case the resource block440 has a dimension of 12 resource elements 450 in the frequencydimension and 7 resource elements 450 in the time dimension, resultingin an overall bandwidth of 12 subcarriers and a duration of 7 symbols.

In operation, data transmissions between a base station and a terminaldevice may be scheduled to use particular resource blocks. Thisscheduling is usually carried out by the base station or a relatednetwork entity. Certain resource blocks may be permanently allocated tocarry predetermined signalling information.

3GPP LTE Releases 8, 9 and 10 (Rel. 8/9/10) define 6 downlinktransmission bandwidth configurations from 1.4 MHz to 20 MHzrepresenting the use of 6, 15, 25, 50, 75 or 100 resource blocks. Asnoted above, all Rel. 8/9/10 terminal devices are required to supportthe maximum single carrier bandwidth of 20 MHz for compliance with theRel. 8/9/10 standards. Nevertheless, for all bandwidth configurationsRel. 8/9/10 has specified that basic physical layer synchronisationsignals (Primary Synchronisation Signals—PSS, and SecondarySynchronisation Signals—SSS), and the most fundamental systeminformation (Master Information Block—MIB) is transmitted using only thecentral 6 resource blocks which are receivable with a 1.4 MHztransceiver. However, in order to receive the remainder of the carriersystem information the terminal device is required to be able to receivethe full bandwidth of the carrier.

However, and as also noted above, for some applications, for example insituations relating to machine type communications (MTC) and/ordedicated messaging networks (DMN), there is a drive to build low costand hence low capability devices. Ideally, device simplification shouldpermit a reduction in required bandwidth of operation as well asreduction of features and throughput. Terminal devices with a lowerbandwidth capability than that specified for Rel. 8/9/10 may mean thatsuch devices are unable to operate properly on Rel. 8/9/10 compliantnetworks which specify higher bandwidth capabilities. For example,terminal devices with a lower bandwidth capability may not even be ableto receive any more system information than that contained in the MIB ofa Rel. 8/9/10 compliant network.

Low capability devices will ideally be able to find and camp-on thecarrier associated with their target dedicated messaging network(s) evenin the presence of Rel. 8/9/10 higher bandwidth carriers. Furthermore,there is a desire that DMN carriers are not swamped by Rel. 8/9/10capable devices camping-on the DMN, even though the Rel. 8/9/10 capabledevices are in the coverage area of a higher bandwidth Rel. 8/9/10carrier which they could otherwise use.

Subordinate Carrier Definition

As described in relation to FIG. 3, the subordinate carrier resources(for use by MTC devices) may be defined by a certain bandwidth in thefrequency domain (frequency band F₂ in FIG. 3 for example) and a certainpattern of time periods in the time domain. The certain pattern of timeperiods may be a sequence of subframes as described above with referenceto FIG. 4. The sequence of subframes may be a sequence of MBSFNsubframes as defined by signalling within SystemInformationBlockType2(SIB2) of the legacy LTE host carrier. However, it will be recognisedthat the subordinate carrier may be delineated by other means, forexample by scheduling by a base station. The pattern of subframes may bea subset (or all) of those subframes reserved by the information elementmbsfh-SubframeConfigList in the host carrier SIB2.

Conveniently, non-MTC UEs will read SIB2 of the legacy LTE host carrierand determine that a configured pattern of subframes are reserved forother purposes (such as MBMS, relay or as in the present case MTCsubordinate carrier operation). The non-MTC UEs will therefore ignorethe subframes allocated to the subordinate carrier. The configuredpattern of reserved subframes is defined in a flexible manner by theinformation element mbsfn-SubframeConfigList.

In particular, mbsfn-SubframeConfigList comprises a set of 1 or moresubframe allocations each of which is defined by the following fragmentof ASN.1 from TS 36.331:

MBSFN-SubframeConfig ::= SEQUENCE { radioframeAllocationPeriodENUMERATED {n1 , n2, n4, n8, n16, n32}, radioframeAllocationOffsetINTEGER (0..7), subframeAllocation CHOICE { oneFrame BIT STRING(SIZE(6)), fourFrames BIT STRING (SIZE(24)) } }

For a given allocation, the “radioframeAllocationPeriod” indicates theperiodicity, in radio frames, with which MBSFN subframes are included inthe allocation, “n1” indicates that MBSFN subframes are present in everyradio frame, while “n2” indicates that MBSFN subframes are present inevery other radio frame. A radioframeAllocationPeriod of “n32” indicatesthat one in every 32 radio frames includes one or more MBSFN subframes.Radio-frames that contain MBSFN subframes occur when equationSystemFrameNumber modradioFrameAllocationPeriod=radioFrameAllocationOffset is satisfied. Inother words, the radioframeAllocationOffset parameter sets an offset fora start position of the repeating pattern of radio frames. ThesubframeAllocation parameter defines the subframes that are allocatedfor MBSFN within the radio frame allocation period defined by theradioFrameAllocationPeriod and the radioFrameAllocationOffsetparameters. The subframe allocation can either be specified for a singleradio frame within the radio frame allocation period (oneFrame) or forfour consecutive radio frames within the radio frame allocation period(four Frames). The subFrameAllocation parameter is a 6 bit (oneFrame) or24 bit (fourFrame) mask, indicating whether each of 6 (oneFrame) or 24(fourFrame) predetermined subframes are to be reserved. The LTEspecification places restrictions on which subframes may be reserved forother purposes by this method, in order that there is no conflict withthe requirement to receive system information and paging. In an FDD LTEsystem one or more of subframes 1, 2, 3, 6, 7 and 8 may be reserved forother purposes. In a TDD LTE system the subframes that may be reservedare 3, 4, 7, 8 and 9. The system frame number can be derived from theMIB of the host carrier.

FIGS. 5A to 5D are example subframe patterns. Each of FIGS. 5 A to 5Dshows a portion of a repeating pattern which could be specified bymbsfn-SubframeConfigList or by a similar pattern specifying function.Four radio frames having ten subframes each are shown in FIGS. 5A to 5D.The subframes are labelled from 0 (zero) to 9 (nine). The shadedsubframes are those allocated to the subordinate carrier, with theunshaded subframes being retained for use on the host carrier. FIG. 5Aschematically illustrates an FDD pattern in whichradioFrameAllocationPeriod is set to n2 (MBSFN subframes present inevery other radio frame), the radioFrameAllocationOffset is 0 (zero) andthe subframeAllocation mask is 111111 (thereby selecting each ofsubframes 1, 2, 3, 6, 7 and 8). It will be appreciated that thissubframe allocation is a “oneFrame” allocation. A longer bit stringwould be used for the subframeAllocation if subframes were to beprovided over four consecutive radio frames.

FIG. 5B schematically illustrates a TDD pattern based on the sameparameters as FIG. 5A. Specifically, radioFrameAllocationPeriod is setto n2 (MBSFN subframes present in every other radio frame), theradioFrameAllocationOffset is 0 (zero) and the subframeAllocation maskis 11111x (thereby selecting each of subframes 3, 4, 7, 8 and 9). Itshould be noted that the last bit of the mask is not used for TDD. Thedifference between FIGS. 5A and 5B results from the different subframesmapped to the bit mask in the FDD and TDD schemes.

FIG. 5C schematically illustrates an FDD pattern in whichradioFrameAllocationPeriod is set to n1 (MBSFN subframes present inevery radio frame), the radioFrameAllocationOffset is 0 (zero) and thesubframeAllocation mask is 101010 (thereby selecting each of subframes1, 3 and 7). It will be appreciated that this subframe 615 allocation isa “oneFrame” allocation. A longer bit string would be used for thesubframeAllocation if subframes were to be provided over fourconsecutive radio frames.

FIG. 5D schematically illustrates a TDD pattern based on the sameparameters as FIG. 5A. Specifically, radioFrameAllocationPeriod is setto n1 (MBSFN subframes present in every radio frame), theradioFrameAllocationOffset is 0 (zero) and the subframeAllocation maskis 10101x (thereby selecting each of subframes 3, 7 and 9). It should benoted that the last bit of the mask is not used for TDD. Again, thedifference between FIGS. 5C and 5D results from the different subframesmapped to the bit mask in the FDD and TDD schemes. All of the patternsshown in FIGS. 5A to 5D will repeat until the mbsfn-SubframeConfigListis altered. The set of allocation patterns specified inmbsfn-SubframeConfigList, which is signalled in SIB2, defines the“reserved set”. A sub-set of the allocation patterns could be used todefine the subordinate earner. Also, two mutually exclusive sub-setscould be used to define two separate subordinate carriers delimited inthe time domain.

It will be appreciated that this mechanism provides a great deal offlexibility in how much carrier resource is to be allocated to thesubordinate carrier, and also how that resource is distributed withrespect to time. The minimum (non-zero) amount of resources (in the timedomain) which can be allocated is 1 in 320 subframes (whenradioframeAllocationPeriod is set to n32 and only one bit is set in thesubframeAllocation bit mask). The maximum amount of resources (in thetime domain) which can be allocated is 192 in 320 subframes (whenradioframeAllocationPeriod is set to n1 and all six bits are set in thesubframeAllocation bit mask). In some implementations the allocationmight be static to provide a fixed resource subordinate carrier. Thefixed resources could in this case be known to a terminal device inadvance. In other implementations the allocation might be dynamic,resulting in a subordinate carrier having a resource allocation whichcan be increased or decreased to for example meet traffic loadingconditions on the subordinate carrier and/or on the host carrier. Theseincreases or decreases could be based on requests from terminal devicesfor additional resource, or based on decisions made at the base stationor a related entity. An increase in the amount of resources allocated tothe subordinate carrier could be achieved either by altering theparameters of an existing subframe allocation as defined above, or byadding a new subframe allocation according to the principles set outabove. A decrease in the amount of resources allocated to thesubordinate carrier could be achieved either by altering the parametersof an existing subframe allocation as defined above, or by removing anexisting subframe allocation.

In other words, it is possible to use multiple subframe allocations toachieve allocation patterns which would not be possible with a singlesubframe allocation, and to provide a simple way of increasing (ordecreasing, if one of multiple subframe allocations is removed) theamount of resources allocated to the subordinate carrier. In oneimplementation, a first subframe allocation with a relatively lowallocation period and subframe allocation could be used to maintain alow resource subordinate carrier which can be camped onto by a lowcapability terminal device, and then further subframe allocations couldbe added to service the communication needs of the low capabilityterminal device when it has successfully camped on. In this way, theresources available to the host carrier are retained at a high level toserve LTE traffic when the subordinate carrier is not in use.

Signalling the presence of the Subordinate Carrier

Certain resource blocks may be used to carry control signallingincluding synchronisation signals and system information. As explainedabove, a problem can therefore arise if essential control signallingfrom the base station is transmitted outside of the frequency rangewhich can be received by a low-capability device. Fortunately, asdescribed above, the synchronisation signals and the Master InformationBlock (MIB) of the system information are present within a frequencyrange which is likely to be receivable by a low-capability device.However, further system information, carried in System InformationBlocks (SIBs), and the associated control signalling may be transmittedat a frequency which cannot be received by the low-capability device.This would cause problems, potentially preventing the low-capabilitydevice from being able to camp on to the network. It will be appreciatedthat not all host carriers will necessary support a subordinate carrier.If a low-capability device attempts to camp-on to a network which doesnot support a subordinate carrier then the camp-on procedure willultimately fail. This is a waste of time and power for thelow-capability device.

It would therefore be desirable to signal to an MTC UE which hasrestricted reception bandwidth the presence of an MTC subordinatecarrier within a larger bandwidth LTE carrier accessible to legacy UEs(LTE Rel. 8/9/10 UEs). It was discussed above that for all LTEbandwidths (Rel. 8/9/10) the basic physical layer synchronisationsignals and the most important system information (Master InformationBlock) is transmitted using only the central 6 resource blocks (72subcarriers). The Master Information Block (MIB) is transmitted in thePhysical Broadcast Channel (PBCH) which is allocated to the central 72subcarriers and to just the first 4 OFDMA symbols of the second slot ofevery 10 ms radio frame. Thus, assuming that the low bandwidth MT UE isable to receive at least 6 resource blocks in the frequency domain, thenthe PBCH (for example the MIB) may be used to signal the presence of anMTC subordinate carrier.

In FIG. 6, a schematic flow diagram of a first part of a camp-onprocedure is shown. At a step A1, an MTC device seeking to camp-on to asubordinate carrier, for example following power-up, seeks to identifyand decode PSS (Primary Synchronisation Signals) and SSS (SecondarySynchronisation Signals) signalling being broadcast in its location.Once the MTC device synchronises to a carrier using the PSS and SSS, theMTC device determines the frame timing and proceeds to decode the PBCHto determine the MIB for the carrier. At a step A2, the MTC devicedetermines whether or not a subordinate carrier indicator flag ispresent in the MIB. The MTC subordinate carrier indicator flag may besignalled in one (or more) of the MIB bits that are spare in LTE Release8/9/10 (10 bits are currently spare). If the MTC device determines thatthe MIB contains a subordinate carrier indicator flag then the camp-onprocess continues at a step A3. If on the other hand the MTC subordinatecarrier indicator flag was found not to be present, then the camp-onprocedure to this carrier would be terminated. This would allow thedevice to decide upon proceeding with camp-on (or not) simply based upondecoding of the legacy LTE MIB, and to discontinue with camp-onimmediately after the decoding of the legacy LTE MIB should thesubordinate carrier indicator flag not be present. As an alternative tousing the MIB to signal the presence of a subordinate carrier, asubordinate carrier indicator signal could be provided at a knowntime/frequency somewhere other than in the MIB. The particulartime/frequency may be defined referentially with respect to the MIB (forexample). The subordinate carrier indicator signal may be relative tothe host carrier PBCH and/or the System Frame Number conveyed in thehost carrier PBCH/MIB. In this case the MTC device would, followingsynchronisation (at the step A1), search for the subordinate carrierindicator signal at the expected time/frequency (at the step A2). If itis found, then the MTC device knows that one (or more) subordinatecarriers are present and continues its discovery of the MTC subordinatecarrier and the subsequent camp-on process.

In either implementation, it will be appreciated that the presence ofthe subordinate carrier indicator is derivable by the MTC device withoutbeing required to decode any system information block (SIB) of the hostcarrier since the MTC device may be unable to receive the host carrierSIBs which are signalled across the full host carrier frequency band F1.

If the MTC device does not find a subordinate carrier associated withthe host carrier, then it may search for and seek to camp-on to anothercarrier by returning to the step A1 to seek to synchronise with anddecode PBCH for a different carrier.

Signalling the Bandwidth of the Subordinate Carrier(s)

Having detected the presence of an MTC subordinate carrier the UE needsto determine the bandwidth of the subordinate carrier in order to beable to read the further system information which will contain the othercharacteristics of the subordinate carrier. There are a number ofalternative ways in which the subordinate carrier bandwidth may besignalled to the MTC UE:

-   -   (1) The simplest method is to fix the bandwidth of the        subordinate carrier in the 3GPP specifications. Having detected        the presence of a subordinate carrier in the manner described        above, the MTC UE would know by definition the MTC subordinate        carrier bandwidth (e.g. 1.4 MHz, 3 MHz or 5 MHZ).    -   (2) The downlink bandwidth of the MTC subordinate carrier may be        signalled in the legacy LTE MIB. For example if the subordinate        carrier indicator flag were signalled in the PBCH by using a 2        bit field, 4 states could be signalled (absence of a subordinate        earner and three different subordinate carrier bandwidths, e.g.        1.4 MHz, 3 MHz and 5 MHZ).    -   (3) The downlink bandwidth (and possibly other characteristics)        of the MTC subordinate carrier could be signalled in a        Subordinate Carrier Master Information Block (scMIB). The scMIB        would be signalled in fixed time/frequency resources, known in        advance to the mobile terminal and preferably defined in the        3GPP specifications. The possibilities for signalling the scMIB        are described in the following section.        Signalling the Subordinate Carrier Master Information Block        (scMIB)

In the above section three methods of determining the downlink bandwidthof an MTC subordinate carrier by an MTC UE have been described. Thefirst two of these methods involve a priori knowledge of when decodingof the subordinate carrier begins. The last of the described methodsinvolves signalling the downlink bandwidth in a Master Information Blockof the subordinate carrier itself.

A Master Information Block may be regarded as collection of parametersgiving values to configurable characteristics of the carrier and otherinformation to achieve/maintain radio frame synchronisation. A MasterInformation Block is required to be supplied in fixed time/frequencyresources and must be received and decoded before a more flexible schemeof downlink message exchange may be employed. According to the abovedescription, at the point at which the UE tries to decode the scMIB, theUE will know:

-   -   That an MTC subordinate carrier is present (from the indicator        flag/signal).    -   The subordinate carrier centre frequency (it may generally be        assumed that this will be the same as the centre frequency of        the host legacy LTE carrier).

In addition the UE may know the MTC subordinate carrier bandwidth, ifthis has been fixed in the specifications, conveyed in the host carrierMIB or conveyed by some other a priori means. In order to receive anddecode the scMIB the UE must be able to determine in which resourceelements it is carried. The number of resource elements used for thescMIB could be related to the subordinate carrier bandwidth or it couldbe fixed (as is the case for the legacy LTE MIB). If the number ofresource elements were defined to be dependent upon the subordinatecarrier bandwidth, this would require the value of the subordinatecarrier bandwidth to be known a priori. There are a limited number ofspare bits available in the legacy host carrier LTE MIB, and so it maybe considered that there are not sufficient available to use 1 or moreof these to carry subordinate carrier bandwidth information. In thiscase, the UE will not have a priori knowledge of the subordinate carrierbandwidth so the UE will be unable to derive the scMIB resource elementsfrom the bandwidth. Accordingly, for the purposes of the followingdescription it is assumed that the scMIB is always signalled in a fixedset of resource elements defined within the 3GPP specifications.Nonetheless, it should be understood that the present invention is notlimited to this, and that in certain implementations the set of resourceelements used to convey the scMIB may not be fixed.

The fixed set of resource elements is contained within a subset (or all)of those subframes reserved by one (or more) of the subframe allocationsconfigured in the information element mbsfn-SubframeConfigList broadcastin the host carrier SIB2. The fixed subframe allocation to convey thescMIB should:

-   -   Be frequent enough to occasion an acceptable latency for        acquisition of the scMIB by MTC UEs.    -   Not be too frequent that excessive resources are consumed from        the host carrier and subordinate carrier.

It should be noted that it is common for MTC devices to exhibit lowmobility and be able to tolerate comparatively high latencies in messagetransmission. However, this may not be the case with all possible MTCtraffic and it is therefore preferable that the frequency of MIBtransmission be fixed within the 3GPP specification and thus cannot beconfigured dependent upon the expected MTC traffic characteristics.

Various fixed characteristics of the scMIB transmission scheme,including the following, should preferably be defined within the 3GPPspecifications:

-   -   The number, periodicity and relationship to host carrier System        Frame Number of the subframes used for scMIB.    -   The level of repetition encoding employed.    -   Within the subframes used, the number and location of resource        elements used to convey the scMIB (that is, exactly which        slot(s), subcarriers and symbols are to be used).

The number of resource elements used for the scMIB will be a function ofthe number of bits of information that must be conveyed by this method,which will be influenced by the further details of the subordinatecarrier design, but the number will also be constrained by the overheadthat this imposes. The System Frame Number, necessary for the UE tomaintain radio frame synchronisation, upon which many LTE higher layerprocesses are dependent, may be read from the host carrier MIB. However,for efficiency reasons it is likely that once the UE synchronises to thesubordinate carrier, it would be undesirable for the UE to have to keepre-reading the host carrier MIB to maintain this information. Thus,System Frame Number is likely to be carried by the scMIB, although theUE might depend upon the host carrier MIB for this information.

Any combination of parameters conforming to and fully resolving thedefinition of MBSFN-SubframeConfig may be chosen to define whichsubframes convey the scMIB. However, use of a single subframe allocationpattern will provide a solution involving least complexity. For examplea single pattern comprising a single subframe allocation once per radioframe allocation period of 32 frames and with an offset value of zeromay be considered adequate to convey the scMIB dependent upon otherdetails of the subordinate carrier design. Alternatively, if more MIBbits are required then a shorter allocation period of, for example, 16or 8 radio frames could be used and/or more subframes per allocationperiod. Note that while the subframes used to convey the scMIB may bedefined by such a subframe allocation pattern or patterns, not all slotsor resource elements in the subframes defined by the pattern(s) arenecessarily used to convey the scMIB. Use of a shorter allocation periodbut sparse use of the resource elements for the scMIB may offer the bestcompromise in relation to scMIB acquisition time and resource overhead.

The subframe allocation pattern or patterns chosen to define thesubframes used for the scMIB will be included in thembsfn-SubframeConfigList of SIB2 of the host carrier in order to reservethese subframes for special use within the context of the host carrier.However, low bandwidth MTC UEs searching for a suitable subordinatecarrier will not be required to read SIB2 of the host carrier to gainthis information, since the subframe allocation pattern(s) for the scMIBwill be fixed and defined in the 3GPP specifications.

Camp-on Procedure

Referring to FIG. 7, the camp-on procedure following the initial stepsshown in FIG. 6 is schematically illustrated. At a step B1 the locationof the scMIB is determined. As discussed above, the location of thescMIB is likely to be fixed in the 3GPP standards, and so the MTC UEwill be able to frame synchronise with the scMIB broadcast by comparingthe location of the scMIB (radio frame and sub-frame known from the 3GPPspecifications) with the current System Frame Number (which the MTC UEcan derive from the host carrier MIB). At a step B2 the scMIB isreceived and decoded, whereby the system information specified thereincan be acquired and used. At a step B3 the bandwidth and centralfrequency of the subordinate carrier is determined. The bandwidth of thesubordinate carrier may be determined by one of the methods describedabove in the section “Signalling the Bandwidth of the SubordinateCarrier(s)”. The central frequency may be assumed to be the same as thatof the host carrier, but in some implementations may have a differentcentral frequency which would need to be signalled to the MTC UE. Thecentral frequency and bandwidth together identify the frequency bandforming the subordinate carrier. Note that if the bandwidth is notdetermined from the scMIB then the step B3 can be performed before (orin parallel with) the steps B1 and B2.

At a step B4, the allocation of subordinate carrier subframes isdetermined. An indication of those subframes allocated to thesubordinate carrier may be specified in the scMIB. As described above,sub-frames are allocated to the subordinate carrier using a subordinatecarrier sub-frame allocation set which determines which sub frameswithin a repeating group of radio frames are allocated to thesubordinate carrier. At a step B5, further system information (SystemInformation Blocks) relating to the subordinate carrier is obtained fromsubframes allocated to the subordinate carrier. This further systeminformation can be used to complete the camp on procedure of the MTC UEto the subordinate carrier at a step B6. The further system informationmay be at a fixed location within the radio resources of the subordinatecarrier, or at a location within the radio resources of the subordinatecarrier which has been scheduled by the base station, or a combinationof both.

In FIG. 8, example signalling on the host carrier and the subordinatecarrier is schematically illustrated. In FIG. 8, eight radio frames 800are shown, each having a central frequency portion 820 usable by boththe host carrier and the subordinate carrier, and outer frequencyportions 810 usable only by the host carrier. In each radio frame, a MIB830 is provided in the central frequency portion 820. The MIB 830 isreadable by devices using both the host carrier and the subordinatecarrier. Devices seeking to use a subordinate carrier may be able todetermine from the MIB 830 whether a subordinate carrier exists based ona flag present in the MIB 830. In an outer frequency portion 810, systeminformation 840 is provided for use by devices served by the hostcarrier. The system information 840 is shown to be outside of thecentral frequency portion 820 and is thus not available to the kind oflow-capability devices intending to use the subordinate carrier. It willbe appreciated that some system information may happen to be transmittedwithin the central frequency portion 820, but this cannot be guaranteed.The system information 840 is provided in the form of System InformationBlocks (SIBs). Unlike the Master Information Block which is broadcast onthe Physical Broadcast Channel (PBCH), the SIBs are mapped onto thePhysical Downlink Shared Channel (PDSCH). Generally, the MasterInformation Block 830 provides sufficient information to gain access tothe first of the System Information Blocks (SIB1), which in turnprovides sufficient information to gain access to SIB2 et seq. SIB2includes parameters relating to the reservation of MBSFN subframes (asdescribed above). Legacy LTE devices using the host carrier willtherefore be informed of the subframes reserved for use by thesubordinate carrier (or for other purposes, for example MBMS or relaybackhaul) when they decode SIB2. They will therefore know that thesesubframes cannot be used and to ignore them. Within the central portion810 of some or all of the radio frames (every other radio frame in thisexample) is a portion 850 allocated to the subordinate carrier. For thesake of clarity the portion 850 shown in FIG. 8 is contiguous, but itwill be appreciated from FIGS. 5A to 5D for example that this may not bethe case. The portions 850 are used to transmit data and signalling tolow capability devices using the subordinate carrier. Within theallocated portion 850 of the first radio frame is a subordinate carrierMIB (scMIB) 860 carrying various information required for a lowcapability device to acquire the remainder of the subordinate carriersystem information.

Within the allocated, portion 850 of the second radio frame is systeminformation 870 relating to the subordinate carrier. This systeminformation 870 provides information required for a terminal device tocamp on to the subordinate carrier. It will be appreciated that thelocations of the scMIB 860 and the system information 870 is purelyexemplary. The important point is that the scMIB 860 and the systeminformation 870 are conveyed in the allocated portions 850. As describedin detail above, the location and periodicity of the scMIB wouldprobably be fixed (predetermined). The system information 870, whichcould be conveyed in the form of System Information Blocks in a similarmanner to with the host carrier, may be predetermined, or dynamicallyallocated (scheduled), depending on implementation.

In the host carrier, the MIB and any associated SIBs together providethe parameters necessary for system access using the host carrier.Similarly, in the subordinate carrier, the scMIB and any associated SIBscarried in subframes allocated to the subordinate carrier provide theparameters necessary for system access using the subordinate carrier. Inboth cases, the UE (legacy or MTC) requires the MIB to decode the sharedchannel (and thus access SIBs). The MIB contains downlink systembandwidth of the host carrier and the system frame number.

The above embodiment describe a method of conveying a subordinatecarrier for low bandwidth devices within a portion of a larger hostcarrier using for example MBSFN subframe allocation pattern(s) toreserve subframes for the subordinate carrier. This permits a flexibleand efficient definition of a subordinate carrier within a host carrier.An indication of the presence of the MTC subordinate carrier is providedusing a flag in the host carrier MIB. This may require the 3GPP standardto be updated, but will not require any change to legacy LTE devicesbecause the flag is set in current spare bits which can and will beignored by a legacy device. Various methods of signalling subordinatecarrier downlink bandwidth have been described, including fixing the MTCsubordinate carrier bandwidth in 3GPP specifications, signalling thesubordinate carrier downlink bandwidth via a field in host carrier MIB,or signalling using a bit field within the subordinate carrier MIB(scMIB). A method of defining the subframes used for the subordinatecarrier Master Information Block by using fixed (defined in 3GPPspecifications) subframe allocation pattern(s) in relation to the SystemFrame Number of the host carrier has also been described above. Asubordinate carrier has been described (in one example) to be specifiedusing a repeating pattern of sub-frames. A mechanism to specify thisalready exists in LTE, originally for the purpose of specifyingsub-frames for use in MBSFN.

It will be appreciated that various modifications can be made to theembodiments described above without departing from the scope of thepresent invention as defined in the appended claims. In particularalthough embodiments of the invention have been described with referenceto an LTE mobile radio network, it will be appreciated that the presentinvention can be applied to other forms of network such as GSM, 3G/UMTS,CDMA2000, etc. The term MTC terminal as used herein can be replaced withuser equipment (UE), mobile communications device, mobile terminal etc.Furthermore, although the term base station has been usedinterchangeably with e-nodeB it should be understood that there is nodifference in functionality between these network entities.

Further particular and preferred aspects of the present invention areset out in the accompanying independent and dependent claims. It will beappreciated that features of the dependent claims may be combined withfeatures of the independent claims in combinations other than thoseexplicitly set out in the claims.

REFERENCES

-   [1] Holma H. and Toskala A. “LTE for UMTS OFDMA and SC-FDMA based    radio access”, John Wiley and Sons, 2009.

What is claimed is:
 1. A base station (BS) comprising: a transceiver;and a processor, operatively coupled to the transceiver; wherein thetransceiver and the processor are configured to transmit a primarysynchronization signal (PSS), a secondary synchronization signal (SSS),and a physical broadcast channel (PBCH) including a master informationblock (MIB), the PSS, SSS and PBCH are in a first bandwidth of a cellhaving a cell bandwidth, wherein the first bandwidth is a first portionof the cell bandwidth, wherein the MIB includes an indication offrequency resources and time resources for use by user equipments (UEs)to acquire additional system information; and the transceiver and theprocessor are configured to transmit control information using theindication of the frequency resources and the time resources for the UEsto acquire the additional system information.
 2. The BS of claim 1wherein the indication of the frequency resources and the time resourcesis within a first portion of the cell bandwidth.
 3. The BS of claim 1wherein the transceiver and the processor are configured to transmitcontrol information and physical downlink shared channel (PDSCH)transmissions within the first portion of the cell bandwidth and not inother portions of the cell bandwidth.
 4. The BS of claim 2 wherein thetransceiver and the processor are configured to transmit controlinformation indicating a plurality of bandwidth portions of the cellbandwidth, wherein the plurality of bandwidth portions includes thefirst portion.
 5. The BS of claim 4 wherein the transceiver and theprocessor are configured to switch between the plurality of bandwidthportions at different times.
 6. The BS of claim 1 wherein the indicatedfrequency resources and the time resources include control informationfor use by UEs to acquire a system information block
 1. 7. The BS ofclaim 1 wherein the indicated frequency resources and the time resourcesinclude a second MIB.
 8. A method performed by a base station (BS), themethod comprising: transmitting a primary synchronization signal (PSS),a secondary synchronization signal (SSS), and a physical broadcastchannel (PBCH) including a master information block (MIB), the PSS, SSSand PBCH are in a first bandwidth of a cell having a cell bandwidth,wherein the first bandwidth is a first portion of the cell bandwidth,wherein the MIB includes an indication of frequency resources and timeresources for use by user equipments (UEs) to acquire additional systeminformation; and transmitting control information using the indicationof the frequency resources and the time resources for the UEs to acquireadditional system information.
 9. The method of claim 8 wherein theindication of the frequency resources and the time resources is within afirst portion of the cell bandwidth.
 10. The method of claim 8, furthercomprising: transmitting control information and physical downlinkshared channel (PDSCH) transmissions within the first portion of thecell bandwidth and not in other portions of the cell bandwidth.
 11. Themethod of claim 9, further comprising: transmitting control informationindicating a plurality of bandwidth portions of the cell bandwidth,wherein the plurality of bandwidth portions includes the first portion.12. The method of claim 11, further comprising: switching between theplurality of bandwidth portions at different times.
 13. The method ofclaim 8 wherein the indicated frequency resources and the time resourcesinclude control information for use by UEs to acquire a systeminformation block
 1. 14. The method of claim 8 wherein the indicatedfrequency resources and the time resources include a second MIB.
 15. Atleast one non-transient computer readable medium containing programinstructions to perform a method of: transmitting a primarysynchronization signal (PSS), a secondary synchronization signal (SSS),and a physical broadcast channel (PBCH) including a master informationblock (MIB), the PSS, SSS and PBCH are in a first bandwidth of a cellhaving a cell bandwidth, wherein the first bandwidth is a first portionof the cell bandwidth, wherein the MIB includes an indication offrequency resources and time resources for use by user equipments (UEs)to acquire additional system information; and transmitting controlinformation using the indication of the frequency resources and the timeresources for the UEs to acquire additional system information.
 16. Theat least one non-transient computer readable medium of claim 15 whereinthe indication of the frequency resources and the time resources iswithin a first portion of the cell bandwidth.
 17. The at least onenon-transient computer readable medium of claim 15, further comprising:transmitting control information and physical downlink shared channel(PDSCH) transmissions within the first portion of the cell bandwidth andnot in other portions of the cell bandwidth.
 18. The at least onenon-transient computer readable medium of claim 16, further comprising:transmitting control information indicating a plurality of bandwidthportions of the cell bandwidth, wherein the plurality of bandwidthportions includes the first portion.
 19. The at least one non-transientcomputer readable medium of claim 18, further comprising: switchingbetween the plurality of bandwidth portions at different times.
 20. Theat least one non-transient computer readable medium of claim 15 whereinthe indicated frequency resources and the time resources include controlinformation for use by UEs to acquire a system information block
 1. 21.The at least one non-transient computer readable medium of claim 15wherein the indicated frequency resources and the time resources includea second MIB.